Building blocks have developed over time. Originally, solid bricks were used. These evolved into cinder blocks. These blocks are formed of concrete and have a pair of holes formed through the blocks. A typical cinder block is shown in FIG. 1 of U.S. Pat. No. 1,567,430 to Eberling. Another type of cinder block is shown in FIG. 1 of U.S. Pat. No. 2,172,052 to Robbins. The holes in the cinder blocks make the blocks considerably lighter, can be used as a better handle to help carry and position the blocks, can be used as a space within the blocks to hold reinforcing bars, and can be filled with concrete once the blocks are placed.
The basic cinder block has changed little over time. However, new blocks have been developed to make construction more flexible. For example, in U.S. Pat. No. 4,982,544 to Smith, there are disclosed precast concrete modules for use in constructing load-bearing retaining walls—i.e., walls capable of supporting large vertical loads. The Smith precast concrete modules comprise a plurality of face walls and integrally formed connecting walls configured to form cavities in the modules. When the Smith precast concrete modules are assembled into a load-bearing wall, concrete may be poured into each cavity to finally form the load-bearing wall.
A number of blocks were developed to better insulate block walls. A normal cinder block that is filled with cement has no space for insulating material. Although the blocks do provide some insulating properties, such blocks are best known as heat absorbers. Thus, a block wall absorbs heat in the summer and holds that heat, which causes an increased cooling load. Similarly, in winter, they absorb cold, increasing the heating load. To solve this problem, several blocks have been developed to allow for insulative material to be placed within the blocks, thereby breaking the thermal flow paths. Examples of these blocks are found in the following U.S. patents. U.S. Pat. No. 3,593,480 teaches a block that has an outer appearance that is similar to an ordinary cinder block. The block is actually a plastic shell that has cavities that are filled with concrete. The block also has open areas that can be either dead air space or can be filled with insulating material. The problem with these blocks is that they must be filled with concrete, and the concrete must be cured, before they can be set into place. Once filled, these blocks become heavy and are difficult to work with.
U.S. Pat. No. 4,380,887 to Lee teaches a cinder block that is made with special slots that allow foam insulation to be inserted into the slots. The idea is to break up the thermal conductivity through the block webs. Although this design is an improvement, it still requires a full size block, with all the weight problems associated with that. Moreover, the insulating panels are designed to be inserted from both the top and the bottom of the block. This slows down the construction process, if the blocks are insulated in the field. It adds to the cost of installation if the insulation is added at the factory.
U.S. Pat. No. 4,498,266 to Perreton teaches a cinder block that has a center channel to hold blocks of insulation. U.S. Pat. No. 4,745,720 to Taylor teaches a cinder block that is cut in two lengthwise. The split block is then reassembled with a special insulating channel in the center. Special clips are provided to secure the insulation within the block. U.S. Pat. Nos. 5,209,037 and 5,321,926 teach cinder blocks that have complex curves formed in them to receive insulation. Although these blocks provide improved insulating capabilities, the complex curved design increases cost and provides minimal hand holds for block placement. This makes construction more difficult and slow, which also drives up cost.
U.S. Pat. No. 4,841,707 to Nova teaches an alternative direction in block wall construction. As noted above, the problem with ordinary blocks is the transmission of cold and heat through the blocks themselves. The blocks above seek to break the transmission path. Another way to do this is to use a double wall. Such a wall has the outward appearance of an ordinary block wall, but has an outer block wall and an inner block wall that are connected by bracing. The space between the walls can be filled with insulating material to provide the best possible levels of insulation. The problem with the Nova wall is that there are no discrete blocks. Both walls are poured. Although this is an acceptable building method, it can be expensive, especially for residential type construction.
Finally, in U.S. Pat. No. 4,180,956 to Gross, there is disclosed a cavity wall structure comprising hollow panel units 2 interconnected by ties 13, and enclosing insulating elements 11. The Gross wall structure, however, appears to have limited applicability in the construction of load-bearing walls. Gross FIG. 1 shows wall panel units 2 to be much thinner than insulating elements 11. The Gross wall panel units 2 thus appear unsuited for supporting heavy loads, and it is not clear how they would conform to conventional U.S. building code structural requirements because of their relative thinness. Furthermore, components of the Gross wall structure are interconnected with ties 13 located at panel unit edges that not only tie together opposed inner and outer walls but link adjacent wall unit edges. This makes the Gross wall system inapplicable in wall construction projects where construction personnel are trained in building walls by laying discrete blocks with mortar interconnections. A person building one of Gross' walls would need to deal with several separate panel units 2 (adjacent as well as opposed) and ties 13 that would have to be assembled at the same time as the stacking of the insulating elements 11. It is not clear that one person working alone could easily perform this assembly.